Bevel gear drive

ABSTRACT

A bevel gear transmission without shims, especially for a controllable wheel of a service vehicle such as a lift truck, with a one-piece housing for the acceptance of a bevel gearset, a plurality of bearing borings, for the support of a pinion gear shaft, a UniPack bearing and a sealing cover. The sealing cover ( 2 ) is placed at a position at which the vertical borings ( 3, 4 ) for the bearings ( 5, 6 ) of the pinion gear shaft ( 7 ) are to be placed, and the cover being provided with a circumferential protrusion ( 8 ), which enables that an appropriately dimensioned tool can be vertically introduced into the one-piece housing ( 1 ) for a precise construction of the housing which is designed to the closely tolerated dimensions of sections (A) and (B).

This application is a national stage completion of PCT/EP2004/006119filed Jun. 7, 2004 which claims priority from German Application SerialNo. 103 30 032.5 filed Jul. 3, 2003.

FIELD OF THE INVENTION

The present invention concerns a bevel gear transmission without shimsor adjustment spacers and especially concerns a bevel gear transmissionfor one controllable wheel of a service vehicle, such as a fork lifttruck. The bevel gear transmission possesses a one-piece housing toconfine a set of bevel gears, a crown gear and a plurality of boringsfor the support of a bevel pinion shaft.

BACKGROUND OF THE INVENTION

DE-A-198 26 067 makes known a transmission for one steerable drive wheelof a service vehicle with a transmission housing, which can be mountedin a vehicle chassis and pivots about a vertical axis. An electric motorsurmounts this housing, its drive shaft axis being coaxial to the pivotaxis. The motor output is controlled by a spur gear stage comprised of apinion and a spur gear. Further, the gearing includes a second ratiostage determined by a pinion shaft and a crown gear, whereby the pinionof the spur gear stage can be non-rotatably bound to the output shaft ofthe electric motor. Also, the spur gear is non-rotatably connected tothe vertical pinion shaft of the second ratio stage, and the crown gearof the second ratio stage can be non-rotatably affixed to the drivewheel by way of a horizontal output shaft.

Upon acceleration or sudden braking of the service vehicle, the requiredhigh ratio of the second ratio stage activates a substantial reactionforce on the pinion bearing. In a case of increasing loadingrequirements, the load capacity of the pinion bearing and the activetoothing nears a maximum. In order that greater loading may be carried,without increasing outside dimensioning, the second ratio stage of thisknown transmission has been designed as a hypoid gearset with a positiveaxle offset. In this way, it becomes possible to increase the loading,especially on the bearing of the pinion and its toothing.

The transmission, inclusive of the drive wheel, is installed to bepivotally supported in bearings about a vertical motor axle in theservice vehicle. The inner ring of the pivotal bearing is integratedinto the upper part of a housing component, which, together with thelower housing section forms the complete housing. A pinion of a spurgear/pinion combination is affixed to the motor shaft, wherein thispinion meshes with a spur gear, which is fastened on a free, upper endof a vertical pinion shaft belonging to a hypoid gearset. The toothedarea of the hypoid pinion is located at the free lower end of the pinionshaft, which in turn is supported by two roller bearings in the lowerpart of the housing. The crown gear of the hypoid gearset isnon-rotatably bound with a horizontal output shaft by way of a force-fitconnection, that is, a bevel press-fit. The horizontal output shaft issupported in the lower part of the housing and is connected to thecircumference of the drive wheel.

EP-A-1 285 803 teaches of a single wheel drive arrangement, which islikewise designed for service vehicles. This design is powered by aflanged drive motor driving a controllable wheel operating from atransmission housing and comprises at least one gear stage. In order tohold the construction space as small as possible and to simplifymounting and disassembly, the controllable wheel is non-rotatingly anddirectly connected with a gear of the transmission. The connected gearitself is rotatably seated on a coaxial, internally located supportelement of the housing. Insofar as the gear is supported to rotate on ahousing pin or is non-rotatably supported on a shaft extension, whichpenetrates the housing, it is possible that the flange shaft with itsbearing elements can be dispensed with, so that a one-part housing canbe used, which requires neither a cover nor bolted sections. With thesame installation space for the transmission, it is possible furtherthat a larger bevel gear can be installed, which can be used for directpower introduction to the controllable wheel.

The transmission itself is of a two stage design, whereby the firststage is applied to the drive motor with a spur gear meshing, while thesecond stage regulates the controllable wheel with a bevel gear mesh.The two transmission stages are bound together by a drive shaftsupported in the housing, while the controllable wheel is non-rotatablebound with the output drive side bevel gear and a controllable wheelgearset and/or the bevel gear, by way of bearing elements on the housingpin or the shaft extension. Since both the spur gear as well as thebevel pinion can be affixed on the drive shaft before the installation,this adjustment assures a good surface wear pattern as well asadvantageous internal clearances for the spiral and circular toothing ofthe designed bevel gear transmission.

The housing is built in one-piece, whereby a first opening to thedriving motor and a second opening to the controllable wheel areprovided. In this way, the mounting and the disassembly of the singlewheel drive works is made easier. The first opening can be closed by athreaded connection with the inner ring of the ring mount bearing afterbeing installed and the second opening is shut by the bevel gear and aclamping cover.

For the required adjustment of the axial position of the bevel piniontoothing, that is to say, of the bevel gear, spacers or shims areappropriate to align the bearing.

This known bevel gear transmission, as well as all other conventionalbevel gear transmissions, are still burdened by the disadvantage, thatthe bevel gearsets, independently of their design, must be continuallyunder adjustment, that means, that the tolerances of the individualconstruction components, which bring about a faultless functioning ofthe bevel gear transmission, including the bevel gearset itself, must beadjusted in such a manner, that a desirable tooth engagement is assured,when considering the desirable surface wear pattern and thecircumferential backlash. To this purpose as already mentioned above inconnection with the known one-wheel transmission disclosed by EP-A-1 285803, a plurality of spacers or shims are necessary, as well as the needfor frequent individual work-steps in which shims must be selected ofunknown specifications.

Further, it has been found to be disadvantageous, that, first, a highdemand for time is called for, not only during the necessary mounting,alignment and the corresponding measurement, but also second, thesubjective attitude of the erector plays a role. Accordingly, an erectorfor the assembly should have a great deal of experience.

It is the purpose of the present invention, to create a bevel geartransmission, which requires no spacers or shims for adjustment duringits assembly.

SUMMARY OF THE INVENTION

In accord with the invention, provision has also been made, that thebevel gear transmission, without shims, especially intended for thecontrollable wheel of a lift truck, with a one-piece housing to confinea bevel gearset, a spur gear, several borings for bearings for thesupport of a pinion gear shaft, a UniPack bearing set, and a sealingcover, wherein the sealing cover is placed at a specified location,wherein vertical bearing borings for the support of the pinion gearshaft are to be made. The sealing cover is also provided with acircumferential protrusion, which enables finding the exact location forthe vertical introduction of an appropriately dimensioned tool into theone-piece housing. This allows for precise construction with very closeclearances in the dimensional structure to be made in the housing.

With this arrangement, not only the advantage will be achieved, thatshim adjustments are eliminated, but also fewer components arenecessary, so that a simpler assembly is gained, which leads tosubstantial economical savings.

Advantageously, the assembly of the housing for the bevel geartransmission, in accord with its dimensioning, is carried out in a jigfor the purpose.

The standard width tolerance of the prefabricated UniPack bearing iscompacted to such a degree, that it, together with the installationdimensions of the crown gear, falls into allowable clearances and causesthe use of the shims to be redundant.

Advantageously, the tolerance window of the circumferential backlash isso increased, that by fabrication of the components with properconsideration of the tolerances, the desired end-dimensioning of theassembly can be assured in a process safe manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 is a schematic cross-section through the invented bevel geartransmission; and

FIG. 2 is a top view onto the sealing cover.

DETAILED DESCRIPTION OF THE INVENTION

Bevel gear transmissions of the kind described in the introductorypassages, as intended for lift trucks and the like, are well known tothe expert. On this account, in the following, only those partsnecessary for the understanding of the invention need be described.

In order to achieve the purpose of the invention, which is to create abevel gear transmission, wherein during its assembly no spacers or shimsare required, as may be inferred from FIG. 1, a one-piece housing 1 isso shaped, that the housing dimensions A and B can be made in a chuck orjig. To carry this out without problems, the sealing cover 2 is shapedso that a circumferential protrusion 8 allows the vertical borings 3, 4for the bearings 5, 6, which support the pinion gear shaft 7 to beprecisely located. As may be seen in FIG. 2, this enables acorrespondingly custom made tool of appropriate dimensions to beintroduced into the one-piece housing 1 in a vertical direction.Thereby, a considerable degree of precision and procedural safety isgained in the assembly of the dimensioned objects A and B, which are tobe built to very close tolerances. This close dimensioning is necessary,in order to mount within the housing 1, a bevel gear transmission, whichdoes not require further adjustment.

Further, the width tolerance of the already, preadjusted bearing 9,which, advantageously, is a UniPack Bearing, is reduced to the extent,that it, together with the crown gear of installation dimensioning EBMT,can be accommodated in the allowable tolerance window. Accordingly, withthis filling, a further shim adjustment is not necessary. On the otherhand, the longitudinal clearance of the bearing 6 need not also bereduced, since its influence, together with that of the dimensioningEBMK of the pinion gear shaft, on the wear pattern and on thecircumferential backlash is very small, due to a reduced bevel angle KW.

As an additional measure, the tolerance window of the circumferentialbacklash is so increased, that in the course of a tolerance-perfectfabrication of the individual components, the specified final assembleddimensioning can be attained.

By way of the invented formulation of the housing for the bevel geartransmission and the therewith possible reduction of the tolerances, abevel gear transmission may be obtained, with which no corrections arenecessary during the assembly process. Further the invented bevel geartransmission is simpler in its assembly than the conventional bevel geartransmission and is less expensive in time and money to fabricate.

REFERENCE NUMERALS

-   -   1 housing    -   2 sealing cover    -   3 boring for bearing    -   4 boring for bearing    -   5 bearing    -   6 bearing    -   7 pinion gear shaft    -   8 circumferential protrusion on 2    -   9 UniPack bearing

1-4. (canceled)
 5. A bevel gear transmission without shims, for acontrollable wheel of a service vehicle, the transmission comprising aone-piece housing to confine a bevel gearset, a crown gear, a pluralityof bearing borings for bearings of a bevel pinion gear shaft, a spurgear stage, which precedes the bevel gearset, and drives the pinion gearshaft, the crown gear is supported by bearings in the housing by aUniPack bearing, and in that the housing is constructed as one-piece andfully confines the bevel gearset and the spur gearing, and the bevelgear transmission possesses a sealing cover, which covers an opening ofthe housing in an area of the spur gearing, the sealing cover (2) isplaced at a location, at which vertical bearing borings (3, 4) for thebearings (5, 6) of the bevel pinion gear shaft (7) are to be made, andsaid sealing cover is provided with a circumferential protrusion (8),which allows an appropriately dimensioned tool to be verticallyintroduced into the one-piece housing (1) for exact boring of precise,close tolerance bearing borings for the tapered pinion gear shafts (A,B), the bearing boring for the bevel pinion gear shaft can be made insaid housing completely in a jig.
 6. The bevel gear transmissionaccording to claim 5, wherein a width tolerance of the UniPack bearing(9) is so limited, that it, together with dimensions (EMBT) of the crowngear falls into an acceptable tolerance window, which advantage causesuse of a shim to be redundant.
 7. The bevel gear transmission accordingto claim 5, wherein a tolerance window of a circumferential back lash isso enlarged, that during an assembly, when consideration is given toproper tolerances, fabrication of individual components results in anassembly which is procedure safe and within limits of specified mounteddimensioning.
 8. A bevel gear transmission without shims, for acontrollable wheel of a service vehicle, the transmission comprising; aone-piece housing to confine a bevel gearset, a crown gear, a pluralityof bearing borings for bearings of a bevel pinion gear shaft, and a spurgear stage, which precedes the bevel gearset, and drives the pinion gearshaft, the crown gear is supported in the housing by a UniPack bearing,the housing fully confines the bevel gearset and the spur gearing; asealing cover of the bevel gear transmission covers an opening of thehousing in an area of the spur gearing, the sealing cover (2) is placedat a location on the housing at which vertical bearing borings (3, 4)for the bearings (5, 6) of the bevel pinion gear shaft (7) are to bemade, and the sealing cover is provided with a circumferentialprotrusion (8), for allowing an appropriately dimensioned tool to bevertically introduced into the housing (1) for exact boring of precise,close tolerance bearing borings for the tapered pinion gear shafts (A,B), the bearing boring for the bevel pinion gear shaft can be made inthe housing completely in a jig.